This invention relates generally to an internal combustion engine and, more particularly, to an EGR/bleed air diverter valve.
An exhaust gas recirculation (EGR) system is used for controlling the generation of undesirable pollutant gases and particulate matter in the operation of internal combustion engines. Such systems have proven particularly useful in internal combustion engines used in motor vehicles such as passenger cars, light duty trucks, and other on-road motor equipment. EGR systems primarily recirculate the exhaust gas by-products into the intake air supply of the internal combustion engine. The exhaust gas that is introduced to the engine cylinder reduces the concentration of oxygen therein, which in turn lowers the maximum combustion temperature within the cylinder and slows the chemical reaction of the combustion process, thereby decreasing the formation of nitrous oxides (NOx). Furthermore, the exhaust gases typically contain unburned hydrocarbons, which are burned on reintroduction into the engine cylinder, which further reduces the emission of exhaust gas by-products which would be emitted as undesirable pollutants from the internal combustion engine.
In many EGR applications, the exhaust gas is diverted by an EGR valve directly from the exhaust manifold. The percentage of the total exhaust flow which is diverted for reintroduction into the intake manifold of an internal combustion engine is known as the EGR flow rate of the engine.
Some internal combustion engines include turbochargers to increase engine performance, and are available in a variety of configurations. For example, fixed housing turbochargers have a fixed exhaust inlet nozzle that accelerates exhaust gas towards a turbine wheel, which in turn rotates a compressor. Also, a variable nozzle turbocharger (VNT) has a variable nozzle having a ring of a plurality of variable vanes which are controlled to change the cross sectional area through which the exhaust gases pass to reach the turbine. In a VNT, the smaller the nozzle opening, the faster the gas velocity to the turbine, and in turn, the higher the boost. Still further, it is known to provide a turbocharger having two independent compressors, which is known as a double sided compressor.
When utilizing EGR in a turbocharged diesel engine, the exhaust gas to be recirculated is often removed upstream of the exhaust gas driven turbine associated with the turbocharger. The recirculated exhaust gas is typically introduced to the intake air stream downstream of the compressor and air-to-air after-cooler (ATAAC). Reintroducing the exhaust gas downstream of the compressor and ATAAC is preferred in some systems due to the reliability and maintainability concerns that arise if the exhaust gas passes through the compressor and ATAAC.
The ability to supply EGR gases into the intake manifold and/or fresh air into the exhaust manifold is a difficult task, considering the high temperatures, exhaust corrosion and abrasion, sealing needs, actuators and packaging constraints of prior EGR systems. For example, U.S. Pat. No. 5,440,880 discloses a diesel engine EGR system having a flow diverter valve positioned immediately downstream of an EGR valve. The flow diverter valve is controlled to modulate the portion of exhaust gas that is directed to an after-cooler to be cooled prior to introduction into the intake manifold, or directs exhaust gas directly to the intake manifold. The exhaust gas that is directed to the after-cooler is first conditioned by an exhaust gas conditioner to remove soot so as to optimize the efficiency of the after-cooler.
At high speed and load, the pressure in the intake manifold will be higher than that of the exhaust manifold. If a passageway is opened between the intake and exhaust manifold under these conditions, fresh air will flood into the exhaust manifold, thereby significantly decreasing the engine performance.
The present invention is directed to overcoming one or more of the problems or disadvantages associated with the prior art.
In one aspect of the invention, a valve is provided for use in an EGR system for an internal combustion engine. The valve has a housing having an exhaust inlet, an EGR outlet, an exhaust outlet and a bleed air inlet. A butterfly plate is pivotally connected to the housing. The butterfly plate has at least a first position and a second position, wherein the first position defines a first fluid path between the exhaust inlet and the EGR outlet and defines a second fluid path between the bleed air inlet and the exhaust outlet, and wherein the second position defines a third fluid path between the exhaust inlet and the exhaust outlet and defines a fourth fluid path between the bleed air inlet and the EGR outlet.
In another aspect of the invention, provided is an internal combustion engine, comprising a block defining a plurality of combustion cylinders, the plurality of combustion cylinders having a first group of combustion cylinders and at least one EGR pumping cylinder. An intake manifold is connected to the block for providing combustion air to each of the plurality of combustion cylinders. A first exhaust manifold is connected to the block to receive combustion gases from the first group of combustion cylinders. A second exhaust manifold is connected to the block to receive combustion gases from the at least one EGR pumping cylinder. A turbocharger has a turbine and a compressor. The turbine has an exhaust gas inlet port and an exhaust gas outlet port, the exhaust gas inlet port of the turbine being coupled for fluid communication with at least one of the first exhaust manifold and the second exhaust manifold. A compressed air conduit is coupled to provide fluid communication between a compressed air outlet port of the compressor and the intake manifold. The compressed air conduit has a bleed air port. A valve is provided having a housing and a valve mechanism. The housing has an exhaust inlet, an EGR outlet, an exhaust outlet and a bleed air inlet, the exhaust inlet being connected in fluid communication with the second exhaust manifold, the EGR outlet being connected in fluid communication with the intake manifold, the exhaust outlet being connected in fluid communication with the first exhaust manifold, and the bleed air inlet being connected in fluid communication with the bleed air port of the compressed air conduit. The valve mechanism has at least a first position and a second position. The first position defines a first fluid path between the exhaust inlet and the EGR outlet and defines a second fluid path between the bleed air inlet and the exhaust outlet. The second position defines a third fluid path between the exhaust inlet and the exhaust outlet and defines a fourth fluid path between the bleed air inlet and the EGR outlet.
In still another aspect of the invention, provided is a method of providing EGR for an internal combustion engine, comprising the steps of providing a single valve having a housing and a valve mechanism, the housing having an exhaust inlet, an EGR outlet, an exhaust outlet and a bleed air inlet; positioning the valve mechanism in a first position to define a first fluid path between the exhaust inlet and the EGR outlet and to define a second fluid path between the bleed air inlet and the exhaust outlet; positioning the valve mechanism in a second position to define a third fluid path between the exhaust inlet and the exhaust outlet and to define a fourth fluid path between the bleed air inlet and the EGR outlet; and positioning the valve mechanism between the first position and the second position to simultaneously control an amount of EGR gases and an amount of compressed bleed air supplied in the internal combustion engine.